1. Field of the Invention
The present invention relates to a semiconductor integrated circuit. More particularly, it relates to latch terminal. A second input terminal of the third gate circuit each having a circuit for soft-error noise resistance.
2. Description of the Related Art
In charge-coupled-device (CCD) memories and dynamic metal oxide semiconductor (MOS) random access memories (RAMs), a soft-error due to alpha-rays is extensively known. A package for a semiconductor device includes very small amounts of uranium (U) and thorium (Th) which decay and emit alpha-rays. The emitted alpha-rays impinge on a semiconductor chip including integrated circuits and generate a plurality of pairs of electrons and positive-holes, particularly in area in which capacitors or depletion regions are formed. The electrons are gathered in an active region, such as a collector region of a transistor, resulting in the reduction of potential at the collector. This reduction of potential occurs in a very short time-period, for example, several hundreds of picoseconds, but may adversely affect the integrated circuit in the semiconductor chip.
In principle, the above-mentioned soft-error may occur in any semiconductor device. In dynamic MOS RAMs, for example, to overcome the soft-error, counter-measures are taken such as the provision of error-collection circuits (ECCs), alpha-ray shield sheets, etc.
In bipolar semiconductor devices or static MOS RAMs, the above soft-error has not had a serious effect, because they have high operating stability and large amplitudes. Recently, however, the integration of semiconductor devices has greatly increased, resulting in smaller amplitudes and smaller operating currents. As a result, even in bipolar semiconductor devices, including, for example, emitter-coupled logic (ECL) circuits and transistor-transistor-logic (TTL) circuits, the effects of soft-error must be taken into account.
Latch circuits are extensively used in semiconductor devices. For example, in a gate array semiconductor device, latch circuits are used for holding input or output data or temporary inner data storage, or the like. In a memory device, latch circuits are used for holding control data, or the like. If latch circuits are affected by a soft-error, the held data may be destroyed, causing troublesome problems such as error signal output. Therefore, latch circuits of the bipolar type or other type must be free from alpha-rays.
Known circuits for overcoming soft-errors, however, cannot be applied to latch circuits, because latch circuits must maintain high speed response and must have a simple structure.